1. Field of the Invention:
The present invention relates to novel plasmapheresis technique, and, more especially, to novel plasmapheresis process/apparatus for the withdrawal/return of body fluid from/to a patient and requiring but a single needle injection therefor.
2. Description of the Prior Art:
Plasmapheresis is a known technique entailing separating the whole blood of a donor into two fractions, the first fraction constituting the plasma phase, while the second fraction constitutes the cellular phase which is typically reinjected back into the donor. The plasma phase is a complex aqueous solution containing protein in particular, while the cellular phase, still containing some of the plasma, comprises the red blood cells (or erythrocytes), the white blood cells (or leucocytes) and the blood platelets.
The technique of plasmapheresis has long been used for animal experimentation. Compare, for example, John J. Abel et al, "Plasma Removal with Return of Corpuscles", which appeared in 1914 in J. Pharmacol. Exp. Ther., No. 5, pages 625 to 641, in which dog's blood is centrifuged to effect the separation. Cf. the article by A. Geiger which appeared in 1931 in J. Phys., 71, pages 111-120, entitled "Method of Ultrafiltration in vivo", in which there is described a continuous plasmapheresis procedure on a dog, the separation apparatus used including a membrane-containing separator, the membrane being arranged in a spiral and being selected in such fashion as to enable a plasma solution to be obtained which contained the totality of the proteins in the treated blood, if so desired.
Plasmapheresis has also been used in man for a number of years, as indicated by the article "La plasmapherese - Technique - Indications" by Fr. Oberling et al, J. Med. Strasbourg, pp. 227-279 (March, 1968). Plasmapheresis is thus tending to now supercede the total donation of blood since the former technique has the advantage of permitting larger quantities of plasma to be withdrawn from the patient without drawback or disadvantage. Since the elements formed are restored to the donor, the withdrawal sessions can follow each other at shorter time intervals than when blood in its entirety is donated.
Thus, plasmapheresis is a technique of long standing and the subsequent improvements therein concern either centrifugation-based apparatus or membrane-containing apparatus. Among the several improvement patents relating to membrane-containing apparatus, compare Amicon's German Pat. No. 2,100,209 in which is described a container comprising a membrane forming a spiral for the circulation of whole blood withdrawn from a donor and in which pressure is exerted on the blood contained in the container, either by means of a gas, or by means of a syringe plunger subjected to the action of a leaf spring. By comparison with the apparatus of Geiger described above, this apparatus has, on account of its design, the disadvantage of not permitting continuous operation on the patient. U.S. Pat. No. 4,191,182 describes a membrane-containing apparatus and in which the blood continuously withdrawn from the donor is separated into plasma and a cellular fraction which is continuously returned to the donor, this apparatus having as one particular characteristic the ability to allow one portion of the cellular fraction to recirculate in an upstream compartment of the membrane-containing component and the ability to allow the plasma fraction to recirculate in a downstream compartment of the same component. In published International Application No. wo 79/01,121, apparatus is also described which entails permitting the withdrawal of blood from the donor and the reinjection into the donor of the fraction which has not crossed the membrane, in continuous fashion.
However, each apparatus hereinbefore described as allowing continuous plasmapheresis, nonetheless has the particular disadvantage of requiring insertion of a needle into the patient/donor at two different sites, which is obviously rather unpleasant for him.